Molecular and antigenic characterization of porcine rotavirus YM, a possible new rotavirus serotype

Most rotavirus strains require the cation-independent mannose-6-phosphate receptor, sortilin-1, and cathepsins to enter cells

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Rotaviruses require the TGN to LE transporter CI-M6PR for cell entry.

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Sortilin-1 was identified as a cell factor involved in rotavirus replication.

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Rotaviruses require cathepsins also to enter Caco-2 cells.

Cathepsins, endosomal acid proteases, are transported from the trans-Golgi network to late endosomes by the mannose-6-phosphate receptor (M6PR). We have previously demonstrated that some rotavirus strains, like UK, Wa, WI61, DS-1, and YM, require the cation-dependent (CD-) M6PR and cathepsins to enter from late endosomes to the cytoplasm in MA104 cells, while other strains, like the simian strain RRV, which enter cells from maturing endosomes, do not. However, the role of other trans-Golgi network-late endosome transporters, such as the cation-independent (CI-) M6PR and sortillin-1, has not been evaluated. In this work, we found that several rotavirus strains that require the CD-M6PR for cell entry are also dependent on CI-M6PR and sortilin-1. Furthermore, we showed that the infectivity of all these rotavirus strains also requires cathepsins to enter not only MA104 cells, but also human intestinal Caco-2 cells. This study identifies sortilin-1 as a novel cell factor necessary for the infectivity of a virus; in addition, our results strongly suggest that cathepsins could be common cell factors needed for the infectivity of most rotavirus strains.

Polarized rotavirus entry and release from differentiated small intestinal cells

Rotaviruses infect mature enterocytes from small intestine, however most data about their cellular entry are from studies carried out in non-intestinal polarized or non-polarized cell lines. In this work the entry of porcine rotavirus YM strain into small intestinal cell line IPEC-J2 was studied. It was found that YM and the human rotavirus Wa strain infect preferentially from the basolateral cell surface. Cell infection from the apical and basolateral surfaces was dependent on the presence of cholesterol. The treatment with neuraminidase, sucrose, and bafilomycin suggests that there are differences in the receptor usage and entry mechanism of the virus from the apical and basolateral surface. While cell entry is more efficient from basolateral surface, the viruses egressed mainly from the apical cell side.

Great genetic diversity of rotaviruses detected in piglets with diarrhea in Thailand

A total of 491 fecal specimens collected from diarrheic piglets in Thailand from January 2011 to March 2014 were screened for group A rotavirus by RT-PCR assay. The G and P genotypes of the detected rotaviruses were determined by multiplex PCR or nucleotide sequencing. Group A rotaviruses were detected in 113 out of 491 (23.0 %) fecal specimens. A wide variety of G-P genotype combinations were identified, and G4P[13] was the most prevalent genotype combination (29.2 %), followed by G4P[23] (14.1 %), G5P[23] (11.5 %), G4P[6] (9.7 %), G3P[23] (7.0 %), G5P[13] (6.1 %), G3P[13] (4.4 %), G3P[6] (2.7 %), and G5P[6] (2.7 %). In addition, the other G-P combinations were also detected at a low percentage, including G3P[19], G4P[7], G9P[19], G9P[23], G9P[7], G4P[19], and G11P[13] strains. This study indicated that group A rotaviruses are a common causes of diarrhea in piglets and a great diversity of G and P genotype combinations are circulating in piglets in Thailand.

The tyrosine kinase inhibitor genistein induces the detachment of rotavirus particles from the cell surface

Group A rotaviruses are a major cause of severe gastroenteritis in young infants. In this work we evaluated the potential role of protein tyrosine kinases on rotavirus infectivity and viral progeny production. From the broad-spectrum inhibitors tested, only genistein, a flavonoid, inhibited rotavirus infectivity. The inhibition observed was dose and strain dependent, with more than 10-fold IC50 differences for some rotavirus strains, and the effect of the drug was shown to be dependent of their activity as a protein tyrosine kinase inhibitor, since the inactive analogue of genistein, daidzein, had no effect on virus infection. Investigation of the stage of virus replication blocked by the drug showed that it interferes with the early interactions of the virus with receptors and/or co-receptors, since treatment of the cells with genistein promoted the detachment of the virus from the cell surface.

The tight junction protein JAM-A functions as coreceptor for rotavirus entry into MA104 cells

Several molecules have been identified as receptors or coreceptors for rotavirus infection, including glycans, integrins, and hsc70. In this work we report that the tight junction proteins JAM-A, occludin, and ZO-1 play an important role during rotavirus entry into MA104 cells. JAM-A was found to function as coreceptor for rotavirus strains RRV, Wa, and UK, but not for rotavirus YM. Reassortant viruses derived from rotaviruses RRV and YM showed that the virus spike protein VP4 determines the use of JAM-A as coreceptor.

Complete genome analysis of a rare group A rotavirus, G11P[25], isolated from a child in Mumbai, India, reveals interspecies transmission and reassortment with human rotavirus strains

Hospital-based rotavirus surveillance was carried out in Mumbai during 2005-2009. An isolate (B08299) with a rare genotype combination (G11P[25]) was detected. The present study was undertaken to characterize the complete genome of the isolate. B08299 exhibited a G11-P[25]-I12-R1-C1-M1-A1-N1-T1-E1-H1 genotype constellation. Phylogenetic analysis of the 11 gene segments of B08299 revealed that the VP2 and NSP5 genes of B08299 had a human origin, while the VP6 gene represented an I12 genotype of obscure origin. The remaining six genes formed a lineage distinct from human and porcine rotaviruses within genotype 1. Analysis of the structural and non-structural genes suggested that B08299 has evolved by gene reassortment. Our findings provide further evidence that interspecies transmission is an important mechanism involved in the evolution and genetic diversity of human rotaviruses in nature.

Rotaviruses reach late endosomes and require the cation-dependent mannose-6-phosphate receptor and the activity of cathepsin proteases to enter the cell

Rotaviruses (RVs) enter cells through different endocytic pathways. Bovine rotavirus (BRV) UK uses clathrin-mediated endocytosis, while rhesus rotavirus (RRV) employs an endocytic process independent of clathrin and caveolin. Given the differences in the cell internalization pathway used by these viruses, we tested if the intracellular trafficking of BRV UK was the same as that of RRV, which is known to reach maturing endosomes (MEs) to infect the cell. We found that BRV UK also reaches MEs, since its infectivity depends on the function of Rab5, the endosomal sorting complex required for transport (ESCRT), and the formation of endosomal intraluminal vesicles (ILVs). However, unlike RRV, the infectivity of BRV UK was inhibited by knocking down the expression of Rab7, indicating that it has to traffic to late endosomes (LEs) to infect the cell. The requirement for Rab7 was also shared by other RV strains of human and porcine origin. Of interest, most RV strains that reach LEs were also found to depend on the activities of Rab9, the cation-dependent mannose-6-phosphate receptor (CD-M6PR), and cathepsins B, L, and S, suggesting that cellular factors from the trans-Golgi network (TGN) need to be transported by the CD-M6PR to LEs to facilitate RV cell infection. Furthermore, using a collection of UK × RRV reassortant viruses, we found that the dependence of BRV UK on Rab7, Rab9, and CD-M6PR is associated with the spike protein VP4. These findings illustrate the elaborate pathway of RV entry and reveal a new process (Rab9/CD-M6PR/cathepsins) that could be targeted for drug intervention.

IMPORTANCE

Rotavirus is an important etiological agent of severe gastroenteritis in children. In most instances, viruses enter cells through an endocytic pathway that delivers the viral particle to vesicular organelles known as early endosomes (EEs). Some viruses reach the cytoplasm from EEs, where they start to replicate their genome. However, other viruses go deeper into the cell, trafficking from EEs to late endosomes (LEs) to disassemble and reach the cytoplasm. In this work, we show that most RV strains have to traffic to LEs, and the transport of endolysosomal proteases from the Golgi complex to LEs, mediated by the mannose-6-phosphate receptor, is necessary for the virus to exit the vesicular compartment and efficiently start viral replication. We also show that this deep journey into the cell is associated with the virus spike protein VP4. These findings illustrate the elaborate pathway of RV entry that could be used for drug intervention.

The spike protein VP4 defines the endocytic pathway used by rotavirus to enter MA104 cells

Rotaviruses are internalized into MA104 cells by endocytosis, with different endocytic pathways used depending on the virus strain. The bovine rotavirus UK strain enters cells through a clathrin-mediated endocytic process, while the simian rhesus rotavirus (RRV) strain uses a poorly defined endocytic pathway that is clathrin and caveolin independent. The viral surface protein VP7 and the spike protein VP4 interact with cellular receptors during cell binding and penetration. To determine the viral protein that defines the mechanism of internalization, we used a panel of UK × RRV reassortant viruses having different combinations of the viral structural proteins. Characterization of the infectivities of these reassortants in MA104 cells either transfected with a small interfering RNA (siRNA) against the heavy chain of clathrin or incubated with hypertonic medium that destabilizes the clathrin coat clearly showed that VP4 determines the pathway of virus entry. Of interest, the characterization of Nar3, a sialic acid-independent variant of RRV, showed that a single amino acid change in VP4 shifts the route of entry from being clathrin dependent to clathrin independent. Furthermore, characterizations of several additional rotavirus strains that differ in their use of cellular receptors showed that all entered cells by clathrin-mediated endocytosis, suggesting that diverse VP4-cell surface interactions can lead to rotavirus cell entry through this endocytic pathway.

Genomic analysis of human rotavirus strains G6P[14] and G11P[25] isolated from Kolkata in 2009 reveals interspecies transmission and complex reassortment events

In a community based case-control study in Kolkata, India, in 2009, two human rotaviruses with uncommon genotypes G6P[14] and G11P[25] were identified, having bovine and porcine characteristics respectively. Strain N-1/2009 with G6P[14] and strain N-38/2009 with G11P[25] genotypes, were isolated from a 13months aged boy who was asymptomatic and a 10months old girl with severe diarrhea respectively. The remaining 9 gene segments of these two strains were analyzed to find the exact origin of these unusual rotaviruses, and the origin of these two strains from bovine/porcine rotaviruses was apparent. This study identifies zoonotic transmission and single and multiple reassortment events as mechanisms driving the diversity of human rotaviruses. This study indicates interspecies transmission between human and animal rotaviruses causes single or multiple reassortment and thus contribute to the genetic diversity of rotavirus.

Molecular characterization of group A bovine rotavirus in southeastern and central-western Brazil, 2009-2010

Rotavirus is an important cause of neonatal diarrhea in humans and several animal species, including calves. A study was conducted to examine 792 fecal samples collected from calves among 65 dairy and beef herds distributed in two of Brazil's major livestock producing regions, aiming to detect the occurrence of rotavirus and perform a molecular characterization of the rotavirus according to G and P genotypes in these regions. A total of 40 (5.05%) samples tested positive for rotavirus by the polyacrylamide gel electrophoresis (PAGE) technique. The molecular characterization was performed by multiplex semi-nested RT-PCR reactions, which indicated that the associations of genotypes circulating in herds in Brazil's southeastern region were G6P[11], G10P[11], G[-]P[5] + [11], G[-]P[6] in the state of São Paulo and G6P[11], G8P[5], G11P[11], G10P[11] in the state of Minas Gerais. In the central-western region, the genotypes G6P[5] + [11], G6P[5], G8P[-], G6P[11], G [-] P[1], G[-] P[11], and G[-] P[5] were detected in the state of Goiás, while the genotypes G6P[5], G8[P11], G6[P11], G8[P1], G8[P5], G6[P1] were circulating in herds in the state of Mato Grosso do Sul. The genotypic diversity of bovine rotavirus found in each region under study underlines the importance of characterizing the circulating samples in order to devise the most effective prophylactic measures.

Genetic heterogeneity of wild-type G4P[6] porcine rotavirus strains detected in a diarrhea outbreak in a regularly vaccinated pig herd

Group A rotavirus (RV-A) with short electropherotype was identified by ss-PAGE in a neonatal diarrhea outbreak at a Brazilian pig farm where the sows were regularly vaccinated with a commercial vaccine containing OSU (G5P[7]) and Gottfried (G4P[6]) porcine RV-A (PoRV-A) strains. The ss-PAGE positive stool samples (n=20) were characterized as P[6] genotype by multiplex-nested-RT-PCR assay. The nucleotide analysis of the VP4 gene (VP8*) state that the viruses clustered in P[6] lineages that are also shared by RV-A strains identified in human hosts. Nucleotide analysis of the VP7 gene identified different lineages in G4 including a new lineage tentatively designated IX. The immunological pressure induced by commercial vaccine with a rotavirus containing a G4P[6] genotype of porcine origin (Gottfried strain) might have allowed the selection of PoRV-A strains with characteristics found in RV-A strains isolated of human hosts, such as P[6]-Ie and If, and promoted the selection or emergence of RV-A strains with a new lineage of the G4 genotype. The characterization of PoRV-A strains with unusual genotypes described in this study highlight the importance of surveys on the relationship between human and animal rotavirus strains.

Molecular characterization of rotavirus diarrhea among children in South Korea: detection of an unusual G11 strain

Among 312 rotavirus-positive samples collected from eight hospitals across South Korea during 2008 and 2009, the most prevalent circulating G genotype was G1 (35.9%), followed by G3 (24.7%), G2 (17.0%), G4 (7.7%), and G9 (2.6%). Notably, one unusual G11 lineage III strain-the first hypoendemic infection case in the world-was found. Of the P genotypes, P[8] (43.9%) was the most common, followed by P[6] (29.5%), P[4] (9.3%) and P[9] (0.6%). Determining G- and P-type combinations showed that G1P[8] was the most prevalent (20.5%), followed by G2P[6] (12.8%) and G3P[8] (12.8%). These findings provide new information concerning the current prevalence and spread of the rare G11 rotavirus.

Reassortment of human rotavirus gene segments into G11 rotavirus strains

G11 rotaviruses are believed to be of porcine origin. However, a limited number of G11 rotaviruses have been recently isolated from humans in combination with P[25], P[8], P[6], and P[4]. To investigate the evolutionary relationships of these strains, we analyzed the complete genomes of 2 human G11P[25] strains, 2 human G11P[8] strains, and 3 porcine reference strains. Most of the 11 gene segments of these 7 strains belonged to genotype 1 (Wa-like). However, phylogenetic clustering patterns suggested that an unknown G11P[25] strain with a new I12 VP6 genotype was transmitted to the human population, in which it acquired human genotype 1 gene segments through reassortment, resulting in a human G11P[8] rotavirus strain with an entire human Wa-genogroup backbone. This Wa-like backbone is believed to have caused the worldwide spread of human G9 and G12 rotaviruses. G11 human rotavirus strains should be monitored because they may also become major human pathogens.

Molecular characterization of a rare, human-porcine reassortant rotavirus strain, G11P[6], from Ecuador

The Pan-American Health Organization established a rotavirus pre-vaccination disease burden and strain surveillance network in Latin America and the Caribbean in 2004. During strain surveillance in Ecuador in 2005-2006, a rare rotavirus genotype, G11P[6], was detected among common strains. Sequencing and phylogenetic analysis of this strain identified a novel lineage of the G11 VP7 gene, most closely related to A253 (91.8% nt identity), a porcine rotavirus strain identified in Venezuela. Most genes of this strain clustered with porcine, human-porcine or bovine-porcine reassortant strains; only VP6 and perhaps NSP2 genes were more closely related to cognate genes of human rotaviruses. Thus, this strain was likely generated by gene reassortment between porcine and human parental strains. Our study provides further evidence that animal rotaviruses play an important role in genetic and antigenic diversity of rotaviruses pathogenic for humans.

Characterization of a G11,P[4] strain of human rotavirus isolated in South Korea

A novel human rotavirus strain, CUK-1, containing a G11 type combined with a P[4] type was isolated from a 1-year-old female patient with fever and severe diarrhea at Our Lady of Mercy Hospital in Incheon, South Korea. This CUK-1 strain showed the highest degree of nucleic acid similarity (98.7% and 93%) to G11 Dhaka6 and P[4] RV 5, respectively. This novel combined type of CUK-1 rotavirus strain (G11,P[4]) was uncovered from humans and is reported on here for the first time.

A rotavirus strain isolated from pig-tailed macaque (Macaca nemestrina) with diarrhea bears a P6[1]:G8 specificity

A distinct rotavirus strain (PTRV) was isolated in cell cultures from a stool sample obtained from a diarrheic 3-year-old female pig-tailed macaque (Macaca nemestrina) that was born at the breeding colony of the University of Washington in Seattle. Unlike other known simian rotavirus strains including vervet monkey rotavirus SA11 which bears P5B[2]:G3 or P6[1]:G3 specificity, rhesus monkey rotavirus MMU18006 with P5B[3]:G3 specificity, pig-tailed macaque rotavirus YK-1 with P[3]:G3 specificity and rhesus monkey rotavirus TUCH with P[24]:G3 specificity, the cell-culture-grown PTRV strain was shown to bear P6[1]:G8 specificity as determined by VP4 (P)- and VP7 (G)-specific neutralization assays as well as gene sequence analyses. The virus in the original diarrhea stool was also shown to bear genotypes P[1] and G8. In addition, the PTRV strain exhibited a "long" electropherotype, subgroup I specificity and NSP4 genotype A specificity. The PTRV probe formed (i) 8-9 hybrid bands with genomic RNAs of various bovine rotavirus strains and (ii) only 2-3 hybrid bands with simian rotavirus RNAs as demonstrated by RNA-RNA hybridization, suggesting a possible bovine origin of the virus. Serologic analysis of serum samples obtained from selected pig-tailed macaques in the colony suggested that a rotavirus bearing P[1]:G8 specificity was endemic among macaques for at least 8 years (1987-1994). This is the first report describing an isolation of a simian rotavirus bearing a non-G3 VP7 and possibly a P6[1] specificities. Because of its unique simian serotype, this virus may prove to be valuable in challenge studies in a non-human primate model in studies of rotavirus immunity.

Characterization of a novel P[25],G11 human group a rotavirus

A novel rotavirus strain (Dhaka6) isolated from a 21-year-old Bangladeshi male patient was characterized by sequence analysis of its VP7 and VP4 gene segments. Phylogenetic analysis of the VP7 gene of the Dhaka6 strain revealed a common evolutionary lineage with porcine G11 rotavirus strains. This isolate is the first reported G11 rotavirus strain infecting a human host. Comparison of the VP4 gene sequences with all currently recognized 24 different P genotypes revealed only low nucleotide (54 to 71%) and amino acid (52 to 76%) sequence identities. This lack of high sequence similarity in the VP4 gene indicates that the Dhaka6 isolate represents a new group A rotavirus P genotype, to which we propose assignment of the designation P[25].

A porcine G9 rotavirus strain shares neutralization and VP7 phylogenetic sequence lineage 3 characteristics with contemporary human G9 rotavirus strains

Of five globally important VP7 (G) serotypes (G1-4 and 9) of group A rotaviruses (the single most important etiologic agents of infantile diarrhea worldwide), G9 continues to attract considerable attention because of its unique natural history. Serotype G9 rotavirus was isolated from a child with diarrhea first in the United States in 1983 and subsequently in Japan in 1985. Curiously, soon after their detection, G9 rotaviruses were not detected for about a decade in both countries and then reemerged in both countries in the mid-1990s. Unexpectedly, however, such reemerged G9 strains were distinct genetically and molecularly from those isolated in the 1980s. Thus, the origin of the reemerged G9 viruses remains an enigma. Sequence analysis has demonstrated that the G9 rotavirus VP7 gene belongs to one of at least three phylogenetic lineages: lineage 1 (strains isolated in the 1980s in the United States and Japan), lineage 2 (strains first isolated in 1986 and exclusively in India thus far), and lineage 3 (strains that emerged/reemerged in the mid-1990s). Currently, lineage 3 G9 viruses are the most frequently detected G9 strains globally. We characterized a porcine rotavirus (A2 strain) isolated in the United States that was known to belong to the P[7] genotype but had not been serotyped by neutralization. The A2 strain was found to bear serotype G9 and P9 specificities as well as NSP4 [B] and subgroup I characteristics. By VP7-specific neutralization, the porcine G9 strain was more closely related to lineage 3 viruses than to lineage 1 or 2 viruses. Furthermore, by sequence analysis, the A2 VP7 was shown to belong to lineage 3 G9. These findings raise intriguing questions regarding possible explanations for the emergence of variations among the G9 strains.

Single point mutations may affect the serotype reactivity of serotype G11 porcine rotavirus strains: a widening spectrum?

A panel of single and double neutralization-resistant escape mutants of serotype G11 porcine rotavirus strains A253 and YM, selected with G11 monotype- and serotype-specific neutralizing monoclonal antibodies (MAbs) to VP7, was tested in neutralization assays with hyperimmune sera raised against rotavirus strains of different serotypes. Escape mutants with an amino acid substitution in antigenic region A (amino acids [aa] 87 to 101) resulting in a residue identical or chemically similar to those present at the same positions in serotype G3 strains, at positions 87 for strain A253 and 96 for strain YM, were significantly more sensitive than the parental strains to neutralization with sera against some serotype G3 strains. Also, one YM antigenic variant (YM-5E6.1) acquired reactivity by enzyme-linked immunosorbent assay with MAbs 159, 57/8, and YO-1E2, which react with G3 strains, but not with the serotype G11 parental strain YM. Cross-adsorption studies suggested that the observed cross-neutralization by the G3-specific sera was due to the sera containing antibodies reactive with the parental strain plus antibodies reactive with the epitope(s) on the antigenic variant that mimick the serotype G3 specific one(s). Moreover, antibodies reactive with antigenic region F (aa 235 to 242) of VP7 might also be involved since cross-reactivity to serotype G3 was decreased in double mutants carrying an additional mutation, which creates a potential glycosylation site at position 238. Thus, single point mutations can affect the serotype reactivity of G11 porcine rotavirus strains with both monoclonal and polyclonal antibodies and may explain the origin of rotavirus strains with dual serotype specificity based on sequence divergence of VP7.

Cross-reactive, serotype- and monotype-specific neutralization epitopes on VP7 of serotype G3 and G5 porcine rotavirus strains

VP7 specific monoclonal antibodies raised against serotype G5 porcine rotavirus strains isolated in Venezuela showed either a serotype G5- or monotype-specific pattern of reactivity by neutralization against a panel of 53 group A rotavirus isolates representative of all established G serotypes. Monoclonal antibodies raised against two G3 porcine strains were either specific for a subset of porcine G3 strains or reactive with another subset of porcine G3 strains and with most G5 strains. Neither were reactive with G3 strains from other species. Analysis of neutralization resistant mutants selected with these monoclonal antibodies indicated that epitopes defined by cross-reactive, serotype- and monotype-specific monoclonal antibodies overlap functionally and that binding and neutralization by these antibodies depended on specific amino acid residues in the region A or C of VP7. Results indicate that a high degree of monotypic variation occurs among G5 and G3 porcine rotavirus strains and the existence of at least one common epitope shared by G5 and G3 porcine strains, in the major neutralization domain of these VP7s.

Comparative amino acid sequence analysis of the major outer capsid protein (VP7) of porcine rotaviruses with G3 and G5 serotype specificities isolated in Venezuela and Argentina

Seven porcine group A rotavirus strains isolated in Venezuela were shown to be antigenically related to serotype G3 (five strains) or to serotype G5 (two strains), whereas two strains isolated in Argentina were classified as serotype G5. The serological classification of eight of these strains was confirmed by sequence analysis of the gene encoding the VP7 glycoprotein. A high degree of homology was observed among strains belonging to the same G serotype, although some variations in the serotype-specific regions were detected among different strains. Comparison with the published VP7 amino acid sequences of serotype G3 indicated that most porcine rotavirus strains are more closely related to each other and to human rotavirus strains than to rotavirus strains isolated from other species. Amino acid sequence comparison among serotype G5 porcine strains revealed that Venezuelan porcine isolates were more closely related to the American strain OSU, while the Argentinian strains had a higher similarity to the Australian strain TRF-41. This report confirms the worldwide distribution of these G serotypes among the porcine population.

Molecular epidemiology of human rotaviruses in Manipur: genome analysis of rotaviruses of long electropherotype and subgroup I

In 1987/88 a winter outbreak of infantile gastroenteritis occurred in Manipur, India which was mainly due to rotaviruses of long electropherotype and subgroup (SG) I. The VP7 gene of one of these viruses (M48) has been cloned and sequenced. It was found to be very closely related to the VP7 genes of the G2 serotype human rotaviruses RV-5 and S2. Follow-up epidemiology of this event in Manipur during 1989-1992 yielded mainly rotaviruses of more conventional characteristics (94 isolates of SG II and long electropherotype, and 90 isolates of SG I and short electropherotype), but also 6 isolates of SG I with long electropherotype, indicating that these viruses continue to circulate in the Manipur community. One isolate of short electropherotype was of subgroup II, and one long electropherotype isolate reacted with the group A but not with either the subgroup I or subgroup II monoclonal antibodies.

Prevalence of P types among porcine rotaviruses using subgenomic VP4 gene probes

Nucleic acid probes were developed to differentiate VP4 (P) types among porcine rotaviruses. These probes were then used to determine the relative prevalence of P types 6 (Gottfried-like) and 7 (OSU-like) in cultivated rotaviruses and field specimens. The variable regions between bases 205-551 of the VP4 gene of rotavirus strains OSU and Gottfried were amplified by the polymerase chain reaction and radiolabeled with 32P by random primer extension. Radiolabeled probes were tested in a dot blot hybridization assay. The subgenomic probes prepared from VP4 gene detected as little as 5 ng oF rotavirus RNA and were specific for differentiating the two porcine rotavirus P types. The probes were used to determine the P type of several reference rotavirus strains and recently cultivated porcine rotavirus strains. Eight of the 10 cultivated, previously untyped, rotaviruses isolates tested were of P type 7 (OSU-like). Two rotavirus strains neither reacted with OSU nor with the Gottfried probe, therefore, their P type could not be determined. Seventeen out of the 26 rotavirus (65.4%) field samples tested had a P type 6 (Gottfried-like) whereas 5 out of 26 (19.2%) had a P type 7 (OSU-like). Four of the 26 samples (15.4%) reacted neither with the OSU nor with the Gottfried probe and possibly represent previously unrecognized P types in swine. Data in this study suggests that (1) rotaviruses with P type 7 are most common among the cultivated rotaviruses, (2) rotaviruses with P type 6 are the most abundant type of rotavirus in natural infections and (3) rotaviruses with additional P types are also associated with diarrheic swine.

Serotypic differentiation of rotaviruses in field samples from diarrheic pigs by using nucleic acid probes specific for porcine VP4 and human and porcine VP7 genes

Of 216 fecal and intestinal samples collected from nursing or weaned diarrheic pigs in the United States and Canada, 57 were identified as group A rotavirus positive by RNA electrophoresis and silver staining. Fifty-seven and 52 rotavirus-positive samples were analyzed by hybridization with Gottfried and OSU PCR-derived gene 9 and 4 probes, respectively. Only 17 samples were identified with either homologous VP4 (P)- or VP7 (G)-coding genes or both. One rotavirus identified as G4 and P7 was similar to the previously characterized interserotype rotavirus, SB-1A. Additional hybridization analyses were performed with PCR-derived probes prepared from gene 9 cDNA of the human rotaviruses Wa (G1), DS-1 (G2), and P (G3) and of the porcine rotavirus YM (G11). Eleven of 52 samples collected and analyzed from swine in Ohio, California, and Nebraska were identified as G11. No samples with G1-, G2-, or G3-type specificities were detected among the 25 of 57 rotavirus-positive samples analyzed with human rotavirus-derived probes. Further investigations with a PCR-derived gene 4 probe prepared from porcine rotavirus YM revealed hybridization specificities similar to those of the OSU gene 4 probe.

Immunogens of rotaviruses

Rotaviruses cause gastroenteritis in neonates of many animal species including cattle, swine, horses, dogs, cats, chickens and turkeys. Rotavirions are nonenveloped, are about 75 nm in diameter, have a double capsid, and contain 11 double-stranded RNA segments as their genome. Several antigenically distinct groups of rotaviruses have been identified and have been alphabetically designated as A through G. Group A rotaviruses were the first group of rotaviruses isolated and are the most commonly detected rotaviruses in diarrheic animals. Group A rotaviruses have two surface proteins, VP4 and VP7, both of which are important in serotype determination and in inducing neutralizing antibodies and protective immunity. Multiple serotypes of group A rotavirus based on glycoprotein VP7 (designated as G types) and based on VP4 (P types) have been identified. The immune response to rotaviruses is essentially serotype specific, however, cross-reactive or heterotypic epitopes have also been identified. Currently acceptable methods for immunogen quantitation include the induction of neutralizing antibody in host or laboratory animals. The in vivo efficacy of vaccines against rotavirus-associated gastroenteritis remains the standard method against which in vitro methods must be compared. Several animal models have been developed which could potentially be used in evaluating the efficacy of candidate vaccines. Monoclonal antibodies to rotavirus immunogens are also currently available and serve as valuable reagents for in vitro quantitation of rotaviral immunogens.

Characterization of the neutralizing epitopes of VP7 of the Gottfried strain of porcine rotavirus

The neutralization epitopes of the outer capsid protein VP7 of a porcine group A rotavirus were studied by using neutralizing monoclonal antibodies (N-MAbs). Six N-MAbs which were specific for the VP7 protein of the Gottfried strain of porcine rotavirus (serotype G4) were used for analyzing the antigenic sites of VP7. Three different approaches were used for this analysis: testing the serological reactivity of each N-MAb against different G serotypes of human and animal rotaviruses, analyzing N-MAb-resistant viral antigenic variants, and performing a nucleotide sequence analysis of the VP7 gene of each of the viral antigenic variants generated. From the serological analyses, three different reactivity patterns were recognized by plaque reduction virus neutralization and cell culture immunofluorescence tests. A single MAb (RG36H9) reacted with animal rotavirus serotypes G3 and G4 but not with human serotypes G3 and G4. The MAb 57/8 (D. A. Benfield, E. A. Nelson, and Y. Hoshino, p. 111, in Abstr. VIIth Internat. Congr. Virol., 1987, and E. R. Mackow, R. D. Shaw, S. M. Matsui, P. T. Vo, D. A. Benfield, and H. B. Greenberg, Virology 165:511-517, 1988) reacted with animal and human rotavirus serotypes G3 and G4 and also with human serotype G9 and bovine serotype G6. The other four MAbs reacted only with the porcine rotavirus serotype G4. The epitope defined by MAb 57/8 and the epitope defined by the other five MAbs appeared to be partially overlapping or close to each other, as identified by viral antigenic variant analysis. However, data from nucleotide and deduced amino acid sequence analyses of the VP7 of each of the viral antigenic variants showed that these two epitopes constituted a large, single neutralization domain.

The avian rotavirus Ty-1 Vp7 nucleotide and deduced amino acid sequences differ significantly from those of Ch-2 rotavirus

The Vp7 gene of the avian strain Ty-1, which is classified as G7 serotype, was sequenced and the amino acid sequence deduced. The gene is 1065 nucleotides long with a long open reading frame of 987 nucleotides producing a protein 329 amino acids in length. The amino acid homology of the Ty-1 Vp7 protein to that of the avian Ch-2 Vp7 was 70%. The A, B, and C variable epitope regions of Ty-1 were unique compared to those of Ch-2 and other strains representing the 14G serotypes. The low 53% homology of the A and C regions of Ty-1 and Ch-2 would suggest that Ty-1 may be of a different serotype to the G7 reference strain Ch-2.

Electropherotypes, serotypes, and subgroups of equine rotaviruses isolated in Japan

Electropherotypes (ET), serotypes, and subgroups of equine rotaviruses isolated from foals in Japan were determined. The ETs of 136 isolates from 1981 through to 1991 were divided into six groups: ET-A-ET-F. The ET-A, -B, -C, -D, -E, and -F were present in 3, 1, 121, 9, 1, and 1 strains, respectively. Representative viruses of ET-A, -B, -C, and -D were identified as serotype G3. Viruses of ET-E and -F were identified as serotypes G 10 and G 5, respectively. The four representative viruses of serotype G 3 did not belong to either subgroup I or II. The two viruses of serotypes G 5 and G 10 belonged to subgroup I. Serotype G 3 strains possessing ET-C were prevalent among the foals throughout the study period.

Two-way cross-neutralization mediated by a shared P (VP4) serotype between bovine rotavirus strains with distinct G (VP7) serotypes

Among bovine rotavirus strains, there are three G serotypes (G6, G8, and G10) and three P (VP4) serotypes (PB1, PB2, and PB3, which are defined on the basis of strains NCDV, UK, and B223, respectively). Plaque reduction neutralization assays with hyperimmune antisera disclosed two-way antigenic relationships of strain KN-4 with strain KK-3 (G10, PB3) as well as with strains NCDV (G6, PB1) and 0510 (G6, PB2). Neutralization assays with monoclonal antibodies specific for G6, G10, and PB3 revealed that KK-3 and KN-4 had the same P serotype (PB3) but that neither G6- nor G10-specific monoclonal antibody neutralized KN-4. Comparison of the VP7 gene sequence of KN-4 with those of other bovine rotavirus strains indicated that KN-4 was more similar to G6 bovine strains than to KK-3 and other G10 strains, suggesting that the G serotype of KN-4 was G6. From these results, we concluded that the two-way cross-neutralization between KN-4 and NCDV or 0510 was mediated by shared G6 serotype specificity, whereas the two-way cross-neutralization between KN-4 and KK-3 was mediated by shared P serotype specificity (PB3). Thus, KN-4 and KK-3 represent the first reported example of a two-way antigenic relationship mediated only by the P serotype. This article emphasizes the need for adopting a binary serotyping system and development of reagents which will enable classification of rotaviruses based on their G and P serotype specificities.

Amino acid sequence analysis of bovine rotavirus B223 reveals a unique outer capsid protein VP4 and confirms a third bovine VP4 type

The nucleotide and deduced amino acid sequence of the gene 4 of bovine rotavirus strain B223 is described. The open reading frame is predicted to encode a VP4 of 772 amino acids, shorter than described for any other rotavirus strain sequenced to date. B223 VP4 shows 70 to 73% similarity to other rotavirus VP4 proteins, demonstrating the presence of a unique VP4 type, and confirming a third VP4 allele in the bovine rotavirus population. Multiple sequence alignment with several other rotavirus strains created gaps in the sequence to account for a shorter VP4. The alignment shows a two contiguous amino acid deletions within the trypsin cleavage region of B223 VP4. Comparisons of two regions flanking the trypsin cleavage site, (aa 224 to 235, and aa 257 to 271) which show high homologies between strains, demonstrate that the region 5' to the trypsin cut site has a low homology (66%) to other rotavirus strains, although the region 3' to the trypsin cleavage site shows high homologies (86 to 93%) with other rotavirus strains. The lack of a conserved proline residue within the 5' flanking region suggests a possible altered local conformation of this site in B223 VP4. A second gap inserted into the VP4 of B223 on multiple sequence alignment is a three contiguous amino acid deletion at position 613-615 in the VP5* subunit. Previously defined biologic properties of this strain in relation to the determination of the amino acid composition of VP4 are discussed.

Hemagglutination by a human rotavirus isolate as evidence for transmission of animal rotaviruses to humans

Human rotavirus strain Ro1845, which was isolated in 1985 from an Israeli child with diarrhea, has a hemagglutinin that is capable of agglutinating erythrocytes from guinea pigs, sheep, chickens, and humans (group O). Hemagglutination was inhibited after incubation with hyperimmune sera or in the presence of glycophorin, the erythrocyte receptor for animal rotaviruses. These results suggest that Ro1845 is an animal rotavirus that infected a human child.

Human rotavirus strain with unique VP4 neutralization epitopes as a result of natural reassortment between members of the AU-1 and Wa genogroups

Human rotavirus strain K8, which possesses unique VP4 neutralization epitopes, was examined by RNA-RNA hybridization to determine its genogroup. While it possessed four gene segments that formed hybrids with strain Wa (a prototype of the Wa genogroup), strain K8 possessed seven gene segments, including gene segment 4, that formed hybrids with strain AU-1 (a prototype of the AU-1 genogroup) which has been shown to share a unique gene 4 allele with feline rotaviruses. These results suggest that strain K8 is an intergenogroup reassortant formed in nature between a member of the Wa genogroup and a member of the AU-1 genogroup.

Evidence for two serotype G3 subtypes among equine rotaviruses

Ten cultivable equine rotavirus isolates, two of North American, six of British, and two of Irish origin, were compared with standard rotavirus strains and with each other by cross neutralization, neutralization with a panel of monoclonal antibodies (MAbs), hybridization to a simian rotavirus (SA-11) VP7 gene probe, and reaction with rotavirus subgrouping and serotyping MAbs in enzyme-linked immunosorbent assays. Six isolates, two of which had previously been serotyped as G3 by other workers, were found to be serotype G3; one was confirmed to be G5, and three were not related to serotypes G1 to G10. The serotype G3 strains were divisible into two subtypes, G3A and G3B, on the basis of cross neutralization. This division was also apparent in reactions with neutralizing VP7-specific MAbs and in the liquid hybridization assay. Two of the isolates were not bound by either subgroup MAb, six were bound by both subgroup I and II MAbs, and two were bound by only the subgroup I MAb. The assays used in this characterization provide a range of epidemiological information for use in future field investigations.

Rotavirus serotype G3 predominates in horses

Foal fecal group A rotavirus strains were characterized by electropherotype, serotype, and subgroup and shown to be distinctly different from rotaviruses of other mammals. Of 86 strains that were electropherotyped, 98% had similar profiles, with gene segments 3 and 4 close together and segments 7, 8, and 9 widely spaced. Of 70 strains that had sufficient detectable VP7 antigen to be serotyped by enzyme-linked immunosorbent assays (ELISAs), 63% were serotype G3 (39% were subtype G3A and 24% were subtype G3B), 4% were serotype G13, and 33% were untypeable. Serotypes G1, G2, G4, G5, G6, G9, G10, and G14 were not detected, although G5 and G14 strains have been identified among cultivable equine strains. Of 50 strains that had sufficient detectable VP6 antigen to be subgrouped by ELISAs, only 12% were able to be assigned to either subgroup I or II, with the remaining 88% belonging to neither subgroup.

Molecular and serological analyses of two bovine rotaviruses (B-11 and B-60) causing calf scours in Australia

Fecal specimens from 78 calves involved in outbreaks of calf diarrhea which occurred in three farms in Victoria, Australia, in 1988 were analyzed for rotaviruses. Thirty-eight samples were positive for group A virus antigen by enzyme-linked immunosorbent assay, and 20 of these contained viral double-stranded RNAs that could be detected by polyacrylamide gel electrophoresis. Two major electropherotypes could be observed, and a representative isolate of each electropherotype (isolates B-11 and B-60) was successfully adapted to grow in MA104 cells. Sequencing of the VP7 genes directly from RNA transcripts of fecal and cell culture-adapted viruses demonstrated that no base changes occurred in this gene upon adaptation to growth in MA104 cells. Sequencing also revealed that the VP7 protein of B-60 was closely related to G serotype 6 (G6) strains, whereas the B-11 sequence was significantly different from all previously published sequences except the recently reported VP7 sequences of bovine isolates 61A and B223, particularly across the antigenic regions A, B, and C. The other strains most closely related to B-11 by VP7 amino acid sequence analysis were G4 porcine strains BMI-1 and BEN-144 and G8 human strain 69M. Serotyping of B-11 and B-60 gave results that were in good agreement with the sequencing data. Hyperimmune typing sera clearly identified B-60 as a member of G6, whereas the B-11 strain reacted to moderate titers only with antisera to some G10 strains. Antiserum raised against B-11 neutralized some strains of G10 cross-reacted with porcine G4 type isolates BMI-1 and BEN-144 but not with other G4 strains or with rotaviruses of other mammalian G serotypes. Northern blot hybridization showed that B-11 was closely related to the recently reported bovine G10 strain B223, and they both possessed a similar segment 4 that was different from that of either UK bovine or NCDV rotavirus.

Sequence of the VP7 gene of chicken rotavirus Ch2 strain of serotype 7 rotavirus

The gene that encodes the VP7 protein of the Ch2 strain of group A chicken rotavirus (serotype G7) was sequenced, and its deduced amino acid sequence analyzed. The gene is 1067 bp in length and contains a single long open reading frame of 987 nt, capable of encoding a protein of 329 amino acids. Amino acid homology of the chicken rotavirus VP7 to the corresponding protein of rotaviruses representing each of the other twelve G serotypes ranged from 58 to 63%. In addition, the VP7 protein of the Ch2 strain contains a unique amino acid sequence in variable regions VR5 (A), VR7 (B), or VR8 (C), which is consistent with previous studies indicating that these three regions are involved in G serotype specificity. The VP7 protein had amino acid homology of 19 or 33% with that of groups B (ADRV) or C (Cowden) rotavirus strains, respectively. Attempts to produce reassortants in vivo or in vitro between the Ch2 strain and strains belonging to group A or C rotavirus were unsuccessful. The low level of nucleotide identity in the 5' end noncoding region of the VP7 gene between the Ch2 and the group A or C rotaviruses may account for this failure.

Direct serotyping of porcine rotaviruses using VP7-specific monoclonal antibodies by an enzyme immunoassay

Employing a serotyping EIA test using MAbs both cell culture adapted and faecal porcine rotaviruses were classified into serotypes G3, G3/5, G4, and G5. The MAbs have confirmed and extended the serotyping results obtained using polyclonal antisera. These MAbs are therefore potential reagents for serotyping of porcine rotaviruses. Using subgroup specific MAbs serotypes G3, G3/5, and G5 were found to contain subgroup I antigens while G4 rotaviruses contained either subgroup II or subgroup I antigens.

A novel group A rotavirus G serotype: serological and genomic characterization of equine isolate FI23

Equine rotavirus FI23 was shown to be prototypic of a novel G serotype, provisionally G14, by cross-neutralization and VP7 sequence determination. Although distinct, there are as few as six differing amino acid residues (92, 94, 96, 146, 147, and 221) in the VP7 antigenic regions of FI23 and G3 rotaviruses.

Rotavirus YM gene 4: analysis of its deduced amino acid sequence and prediction of the secondary structure of the VP4 protein

We have determined the complete nucleotide sequence of the VP4 gene of porcine rotavirus YM. It is 2,362 nucleotides long, with a single open reading frame coding for a protein of 776 amino acids. A phylogenetic tree was derived from the deduced YM VP4 amino acid sequence and 18 other available VP4 sequences of rotavirus strains belonging to different serotypes and isolated from different animal species. In this tree, VP4 proteins were grouped by the hosts that the corresponding viruses infect rather than by the serotypes they belong to, suggesting that this protein is involved in the host specificity of the viruses. In an attempt to predict the secondary structure of the VP4 protein, we selected the more divergent VP4 sequences and made a secondary structure analysis of each protein. In spite of variations within the individual structures predicted, there was a general structural pattern which suggested the existence of at least two different domains. One, comprising the amino-terminal 63% of the protein, is predicted to be a possible globular domain rich in beta-strands alternated with turns and coils. The second domain, represented by the remaining, carboxy-terminal part of VP4, is rich in long stretches of alpha-helix, one of which, 63 amino acids long, has heptad repeats resembling those found in proteins known to form alpha-helical coiled-coils. The predicted secondary structure correlates well with the available data on the protein accessibility delineated by immunological and biochemical findings and with the spike structure of the protein, which has been determined by cryoelectron microscopy.

VP4 monotype specificities among porcine rotavirus strains of the same VP4 serotype

The porcine rotavirus OSU strain was used to produce monoclonal antibodies (MAbs) directed against the outer capsid protein VP4. From two separate fusions, eight MAbs that inhibited hemagglutination activity of the OSU strain were selected. All MAbs immunoprecipitated both the OSU VP4 protein derived from a lysate of infected MA104 cells and the OSU VP4 protein expressed in Sf9 cells by a recombinant baculovirus. By immunoprecipitation of in vitro-translated OSU gene 4 transcripts of different length, the eight MAbs were found to be specific for the VP8 subunit of VP4. All MAbs neutralized the OSU strain but failed to neutralize human, bovine, and simian rotavirus strains. Antiserum to the expressed OSU VP4 protein was used to study the distribution of VP4 antigenicity among porcine rotaviruses. At least two distinct specificities were identified among 14 rotavirus strains that had been previously assigned to four distinct VP7 serotypes. Five groups of monotype specificities of the VP4 protein were identified by the eight anti-VP4 MAbs among 11 porcine strains that share the same VP4 serotype.

VP4 relationships between porcine and other rotavirus serotypes

VP4 relationship of Australian porcine rotaviruses were identified using genetic reassortants and MAbs. All porcine virus isolates except BEN-144 appeared to share VP4 antigenicity with OSU virus. VP4 and BEN-144 virus (Gottfried-like virus) showed some antigenic relationships with the human neonatal viruses ST-3 and RV-3. In addition, VP4 of porcine CRW-8 showed antigenic relationships with simian SA-11. RRV and also canine K9 viruses, while that of porcine TFR-41 showed at least one way VP4 antigenic relatedness with UK bovine rotavirus. Furthermore, BMI-1 virus which is antigenically similar to an American virus SB1-A (a naturally occurring reassortant) may have arisen similarly by gene reassortment in nature in Australia.

Serotypic differentiation of group A rotaviruses with porcine rotavirus gene 9 probes

The serotypic specificities of Gottfried and OSU porcine rotavirus gene 9 probes were investigated in a dot hybridization assay. The probes were reacted with homologous and heterologous serotypes of group A rotaviruses of human and animal origin. Hybridizations were conducted under relatively low-stringency (52 degrees C, no formamide, 5 x SSC) and high-stringency (52 degrees C, 50% formamide, formamide, 5 x SSC) conditions (1 x SSC is 0.15 M NaCl plus 0.015 M sodium citrate). Under conditions of relatively low stringency, the Gottfried and OSU gene 9 probes demonstrated broad cross-reactivity and were useful in the detection of homologous and heterologous serotypes of group A rotaviruses. Under conditions of relatively high stringency, the Gottfried and OSU gene 9 probes were serotype specific. The Gottfried gene 9 probe (serotype 4) hybridized with homologous Gottfried porcine rotavirus as well as the serotype 4 human rotaviruses ST3 and VA70. The OSU gene 9 probe (serotype 5) hybridized with homologous OSU porcine rotavirus and the serotype 5 equine rotavirus H1. Hybridization was not observed with the antigenically distinct group B and C porcine rotaviruses or with other porcine enteric viruses, including calicivirus and a coronavirus, transmissible gastroenteritis virus, regardless of stringency conditions. Analysis of 14 group A rotavirus-positive field samples resulted in the serotypic differentiation, collectively, of six serotype 4 or 5 porcine rotaviruses. No field samples reacted with both the Gottfried and OSU gene 9 probes.

Nucleotide sequence of VP4 and VP7 genes of human rotaviruses with subgroup I specificity and long RNA pattern: implication for new G serotype specificity

We sequenced the genes coding for the two neutralization proteins, VP4 and VP7, of human rotavirus strains L26 and L27 with subgroup I specificity but the long RNA pattern. The deduced VP7 amino acid sequence of strains L26 and L27 showed a low homology (73.6 to 81.9%) to those of rotavirus strains of the established serotypes. This finding, together with the previous serological characterizations, suggests that the VP7 (G) serotype of the L26 and L27 strains is distinct from those of strains of the previously established serotypes. In contrast, the VP4 sequences of the L26 and L27 strains were quite similar to those of virulent serotype 2 strains (DS-1, S2, and RV-5).